Corrosion resistant aluminum electrode alloy

ABSTRACT

A method is disclosed, which includes the step of preparing an aluminum alloy body for solutionizing. The aluminum alloy body may include not greater than 0.06 wt. % Fe, where at least some Fe is present. The aluminum body may include not greater than 5.0 wt. % Mg. The balance of the aluminum alloy body may be aluminum and unavoidable impurities. The aluminum alloy body may include a first vol. % of Fe-bearing particles. The method may include solutionizing the as-prepared aluminum alloy body. The solutionizing step may include dissolving at least some of the Fe-bearing particles into solid solution, thereby decreasing the first vol. % of Fe-bearing particles to a second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/US2019/016077, filed Jan. 31, 2019, which claims benefit of priority of U.S. Patent Application No. 62/624,317, filed Jan. 31, 2018, each of which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

Broadly, the present disclosure is directed towards aluminum electrode alloys with improved corrosion resistance.

BACKGROUND

Clean, sustainable energy is a global concern. Electrochemical cells are utilized as clean, sustainable energy. By commercially deploying these sustainable forms of energy, it is possible to lower the global dependence on fossil fuels.

SUMMARY OF THE INVENTION

Utilizing aluminum alloy compositions as an aluminum electrode (e.g., anode) alloy product in an electrochemical cell can be evaluated by quantifying and/or qualifying two phenomena: (1) the anodic reaction and (2) the corrosion reaction of the aluminum electrode alloy composition. In the anodic reaction, aluminum reacts with hydroxyl ions which results in the release of electrons, the primary and desirable product of an electrochemical cell. Without being bound by any particular mechanism or theory, it is believed that in the corrosion reaction, the aluminum in the aluminum electrode (e.g., anode) product material is oxidized in the presence of water and as the oxygen in the water reacts with the aluminum, aluminum oxide is formed, generating hydrogen gas (e.g. a byproduct of the corrosion reaction of the aluminum anode alloy composition). In the corrosion reaction, aluminum is consumed without contributing to the production of (creating) electrical energy in the electrochemical cell. Without being bound by a particular mechanism or theory, it is believed that by reducing the amount of corrosion reaction, more aluminum electrode alloy material is available to participate in the anodic reaction, contributing to the longevity of the aluminum electrode alloy product and production of electrical energy by the electrochemical cell.

The extent of corrosion reaction, i.e. the amount of hydrogen generated for an aluminum electrode alloy product used as an anode, is a function of electrolyte temperatures and current densities in the electrochemical cell. As operating temperatures and applied current vary for the operation of the cell, so too does the aluminum electrode alloy composition experience varying instances of high anodic reaction and high corrosion reaction windows within the operating parameters/ranges of the electrolytic cell.

The present disclosure is directed towards aluminum alloys with improved corrosion resistance when employed as an electrode in an electrochemical cell. More specifically, the present disclosure is directed towards iron-containing aluminum anode alloys having compositions including, for example, not greater than 0.06 wt. % Fe not greater than 5.0 wt. % Mg, and a corresponding heat treatment to configure the iron in solid solution, such that the resulting composition is configured with corrosion resistance when evaluated in accordance with hydrogen generation in an electrochemical half-cell test.

In one embodiment, a method may include the step of (a) preparing an aluminum alloy body for solutionizing. In the embodiment, the aluminum alloy body may include not greater than 0.06 wt. % Fe, where at least some Fe is present. In the embodiment, the aluminum alloy body may include not greater than 5.0 wt. % Mg, with the balance being aluminum and unavoidable impurities. In the embodiment, the aluminum alloy product may include a first vol. % of Fe-bearing particles.

In the embodiment, the method may include the step of (b) solutionizing the as-prepared aluminum alloy body. In the embodiment, the solutionizing step (b) may include dissolving at least some of the Fe-bearing particles into solid solution, thereby decreasing the first vol. % of Fe-bearing particles to a second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body. In one embodiment, the Fe-bearing particles may dissolve into a matrix of the aluminum alloy body.

In one embodiment, the method may comprise quenching of the aluminum alloy body. In these embodiments, the solutionizing step may include solution heat treating and quenching, where the quenching may reduce the temperature of the aluminum alloy body at a rate of at least 38° C. per second. To accomplish the solutionizing step, the temperature of the aluminum alloy body immediately before quenching is higher than the temperature of the aluminum alloy body during quenching.

In some embodiments, the quenching may reduce the temperature of the aluminum alloy body at a rate of: at least 93° C. per second; or at least 204° C. per second; or at least 427° C. per second; or at least 871° C. per second or at least 1760° C. per second; or at least 3538° C. per second; or at least 5538° C. per second.

The quenching may be accomplished to bring the aluminum alloy body to a low temperature (e.g., due to a subsequent cold working step). In one embodiment, the quenching may comprise cooling the aluminum alloy body to a temperature of not greater than 93° C. (i.e., the temperature of the aluminum alloy body upon completion of the quenching step is not greater than 93° C.). In another embodiment, the quenching may comprise cooling the aluminum alloy body to a temperature of not greater than 65° C. In yet another embodiment, the quenching may comprise cooling the aluminum alloy body to a temperature of not greater than 38° C. In another embodiment, the quenching may comprise cooling the aluminum alloy body to ambient temperature.

The quenching may be accomplished via any suitable cooling medium. In one embodiment, the quenching may comprise contacting the aluminum alloy body with a gas. In one embodiment, the gas may be air. In one embodiment, the quenching may comprise contacting the aluminum alloy body with a liquid. In one embodiment, the liquid may be aqueous based, such as water or another aqueous based cooling solution. In one embodiment, the liquid may be an oil. In one embodiment, the oil may be hydrocarbon based. In another embodiment, the oil may be silicone based. In other embodiments, ambient air cooling may be used.

In one embodiment, the aluminum alloy body may be suitable for use as an aluminum electrode alloy product.

In one embodiment, the method may include determining, prior to the solutionizing step (b), conditions for the solutionizing step (b). In the embodiment, the conditions may include a soak temperature range of from 515° C. to a Temperature2 (C). In the embodiment, a value of Temperature2 may be dependent on an actual wt. % Mg of the aluminum alloy body. In the embodiment, Temperature2=644.6−[15.73*(actual wt. % Mg)]. In the embodiment, the method may include completing the solutionizing step (b) according to the determining step.

In one embodiment, the method may include selecting a value for a target temperature (° C.) within the soak temperature range. In the embodiment, the conditions may include a soak time range of from Time1 (hours) to Time2 (hours). In the embodiment, Time1=1.2141×10⁸*e{circumflex over ( )}−(0.032516*target temperature), and Time2=1.4467×10¹⁰*e{circumflex over ( )}−(0.032828*target temperature).

In one embodiment, the method may include determining, prior to the solutionizing step (b), conditions for the solutionizing step (b). In the embodiment, the conditions may include a soak temperature within 50° C. and less than a solidus temperature of the as-prepared aluminum alloy body. In the embodiment, the method may include completing the solutionizing step (b) according to the determining step.

In one embodiment of the method, the determined conditions may include a soak temperature that may be: within 40° C. and less than the solidus temperature of the as-prepared aluminum alloy body; or within 30° C. and less than the solidus temperature of the as-prepared aluminum alloy body; or within 20° C. and less than the solidus temperature of the as-prepared aluminum alloy body; or within 10° C. and less than the solidus temperature of the as-prepared aluminum alloy body; or within 5° C. and less than the solidus temperature of the as-prepared aluminum alloy body.

In one embodiment of the method, the second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body may be: at least 5% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body; or at least 10% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body; or at least 25% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body; or at least 50% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body; or at least 75% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body; or at least 90% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body.

In one embodiment of the method, the aluminum alloy body may include at least some Fe. In one embodiment of the method, the Fe may be present in the aluminum alloy body only as an unavoidable impurity. In one embodiment of the method, the Fe may be present in the aluminum alloy body as a purposefully added alloying element.

In one embodiment of the method, the aluminum alloy body may include 20-600 ppm Fe. In one embodiment of the method, the aluminum alloy body may include 20-400 ppm Fe.

In one embodiment of the method, the aluminum alloy body may include Fe in the amount of: at least 1 ppm; at least 5 ppm; at least 10 ppm; at least 20 ppm; at least 30 ppm; at least 40 ppm; at least 50 ppm; at least 70 ppm; at least 95 ppm; at least 100 ppm; at least 150 ppm; at least 182 ppm; at least 200 ppm; at least 250 ppm; at least 300 ppm; at least 350 ppm; at least 400 ppm; at least 450 ppm; at least 500 ppm; at least 550 ppm; or at least 600 ppm Fe.

In one embodiment of the method, the aluminum alloy body may include Fe in the amount of: not greater than 1 ppm; not greater than 5 ppm; not greater than 10 ppm; not greater than 20 ppm; not greater than 30 ppm; not greater than 40 ppm; not greater than 50 ppm; not greater than 70 ppm; not greater than 100 ppm; not greater than 150 ppm; not greater than 182 ppm; not greater than 200 ppm; not greater than 250 ppm; not greater than 300 ppm; not greater than 350 ppm; not greater than 400 ppm; not greater than 450 ppm; not greater than 500 ppm; not greater than 550 ppm; or not greater than 600 ppm Fe.

In one embodiment of the method, the aluminum alloy body may include at least some Mg. In one embodiment of the method, the Mg may be present in the aluminum alloy body only as an unavoidable impurity. In one embodiment of the method, the Mg may be present in the aluminum alloy body as a purposefully added alloying element.

In one embodiment of the method, the aluminum alloy body may include Mg in the amount of: at least 1 ppm; at least 5 ppm; at least 10 ppm; at least 25 ppm; at least 50 ppm; at least 100 ppm; at least 250 ppm; at least 500 ppm; at least 1000 pp; at least 5000 ppm; at least 10000 ppm; at least 15000 ppm; at least 20000 ppm; at least 24200 ppm; at least 24500 ppm; at least 25000 ppm; at least 25200 ppm; at least 25800 ppm; at least 30000 ppm; at least 35000 ppm; at least 40000 ppm; at least 45000 ppm; or at least 50000 ppm Mg.

In one embodiment of the method, the aluminum alloy body may include Mg in the amount of: not greater than 1 ppm; not greater than 5 ppm; not greater than 10 ppm; not greater than 25 ppm; not greater than 50 ppm; not greater than 100 ppm; not greater than 250 ppm; not greater than 500 ppm; not greater than 1000 ppm; not greater than 5000 ppm; not greater than 10000 ppm; not greater than 15000 ppm; not greater than 20000 ppm; not greater than 24200 ppm; not greater than 24500 ppm; not greater than 25000 ppm; not greater than 25200 ppm; not greater than 25800 ppm; not greater than 30000 ppm; not greater than 35000 ppm; not greater than 40000 ppm; not greater than 45000 ppm; or not greater than 50000 ppm Mg.

In one embodiment of the method, the aluminum alloy body may include one of a 1xxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx, and 8xxx aluminum alloy. In one embodiment of the method, the aluminum alloy body may include an aluminum alloy selected from the group consisting of: a 1xxx aluminum alloy, a 3xxx aluminum alloy, and a 5xxx aluminum alloy. In one embodiment, the aluminum alloy body may be a 5xxx aluminum alloy.

In one embodiment of the method, the aluminum alloy body may include an aluminum alloy having at least 90 wt. % Al.

In one embodiment of the method, a corrosion resistance of an as-solutionized aluminum electrode alloy product (i.e., a “sample” aluminum alloy body prepared and solutionized according to one or more embodiments of the methods disclosed herein) may be greater as compared to the corrosion resistance of a reference aluminum electrode alloy product (i.e., a “control” aluminum alloy body prepared in the same manner as the “sample” aluminum alloy body, but not solutionized according to one or more embodiments of the methods disclosed herein), when measured in accordance with an electrochemical cell test.

In one embodiment of the method, the preparing step (a) may include working the aluminum alloy body into a sheet or plate. In the embodiment, the working may include at least one of hot rolling and cold rolling the aluminum alloy body.

In one embodiment of the method, the preparing step (a) may include forming a melt of an aluminum alloy. In the embodiment, the preparing step may include casting the melt to form the aluminum alloy body. In the embodiment, the casting step may include one of direct chill casting, continuous casting, and shape casting.

In one embodiment of the method, the preparing step (a) may include additively manufacturing the aluminum alloy body.

As used herein, “unavoidable impurities” means the presence of an undesirable component. As a non-limiting example, an unavoidable impurity is present in a quantity or amount that is low enough to not change a desired property and/or characteristic (i.e. below a threshold to modify the corrosion resistance of the corrosion resistant aluminum electrode alloy and/or reduce the corrosion resistance below a certain margin of improvement when compared to the reference aluminum electrode alloy material evaluated in an electrochemical cell test).

As used herein, “solutionize,” “solutionizing,” “solution heat treatment,” and the like, means heating an aluminum alloy body to a suitable temperature, generally above the solvus temperature, holding at that temperature long enough to allow soluble elements to enter into solid solution, and cooling rapidly enough to hold the elements in solid solution. The solid solution formed at high temperature may be retained in a supersaturated state by cooling with sufficient rapidity to restrict the precipitation of the solute atoms as coarse, incoherent particles. “Solutionizing” may include quenching of the aluminum alloy body, which quenching may be accomplished via a liquid (e.g., via an aqueous or organic solution), a gas (e.g., air cooling), or even a solid (e.g., cooled solids on one or more sides of the aluminum alloy body). In one embodiment, the quenching step may include contacting the aluminum alloy body with a liquid or a gas. In some of these embodiments, the quenching may occur in the absence of hot working and/or cold working of the aluminum alloy body. For example, the quenching may occur by immersion, spraying and/or jet drying, among other techniques, and in the absence of deformation of the aluminum alloy body.

As used herein, “soak temperature” means the temperature or range of temperatures at which the aluminum alloy body is held during solution heat treatment.

As used herein, “soak time” means the residence time or range of residence times for which the aluminum alloy body is held at the soak temperature during solution heat treatment.

As used herein, “reference aluminum electrode alloy” means an iron-containing aluminum alloy in an aluminum alloy body prepared according to disclosed preparing step (a), but without being subject to the disclosed solutionizing step (b) of the method described herein.

As used herein, “reference aluminum electrode alloy product” means an aluminum electrode (e.g., anode) alloy product formed from the reference aluminum electrode alloy.

The figures constitute a part of this specification and include illustrative embodiments of the present disclosure and illustrate various objects and features thereof. In addition, any measurements, specifications and the like shown in the figures are intended to be illustrative, and not restrictive. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

Among those benefits and improvements that have been disclosed, other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention is intended to be illustrative, and not restrictive.

Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases “in one embodiment” and “in some embodiments” as used herein do not necessarily refer to the same embodiment(s), though it may. Furthermore, the phrases “in another embodiment” and “in some other embodiments” as used herein do not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

In addition, as used herein, the term “or” is an inclusive “or” operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on”.

Aspects of the invention will now be described with reference to the following numbered clauses:

-   -   1. A method comprising the steps of (a) preparing an aluminum         alloy body for solutionizing, wherein the aluminum alloy body         comprises: (i) not greater than 0.06 wt. % Fe, wherein at least         some Fe is present; (ii) not greater than 5.0 wt. % Mg; (iii)         the balance aluminum and unavoidable impurities; and (iv) a         first vol. % of Fe-bearing particles; and (b) solutionizing the         as-prepared aluminum alloy body, wherein the solutionizing         step (b) comprises dissolving at least some of the Fe-bearing         particles into solid solution, thereby decreasing the first vol.         % of Fe-bearing particles to a second vol. % of Fe-bearing         particles in the as-solutionized aluminum alloy body.     -   2. The method of clause 1, wherein the aluminum alloy body is         suitable for use as an aluminum electrode alloy product.     -   3. The method of any preceding clause, wherein the method         comprises determining, prior to the solutionizing step (b),         conditions for the solutionizing step (b), wherein: (i) the         conditions include a soak temperature range of from 515° C. to a         Temperature2 (° C.); (ii) a value of Temperature2 is dependent         on an actual wt. % Mg of the aluminum alloy body; and (iii)         Temperature2=644.6−[15.73*(actual wt. % Mg)]; and wherein the         method comprises completing the solutionizing step (b) according         to the determining step.     -   4. The method of any preceding clause, wherein the method         comprises selecting a value for a target temperature (° C.)         within the soak temperature range, wherein: (i) the conditions         include a soak time range of from Time1 (hours) to Time2         (hours); (ii) Time1=1.2141×10⁸*e{circumflex over         ( )}−(0.032516*target temperature); and (iii)         Time2=1.4467×10¹⁰*e{circumflex over ( )}−(0.032828*target         temperature).     -   5. The method of any preceding clause, wherein the method         comprises determining, prior to the solutionizing step (b),         conditions for the solutionizing step (b), wherein: (i) the         conditions include a soak temperature within 50° C. and less         than a solidus temperature of the as-prepared aluminum alloy         body; and wherein the method comprises completing the         solutionizing step (b) according to the determining step.     -   6. The method of any preceding clause, wherein the soak         temperature is within 40° C. and less than the solidus         temperature of the as-prepared aluminum alloy body.     -   7. The method of any preceding clause, wherein the soak         temperature is within 30° C. and less than the solidus         temperature of the as-prepared aluminum alloy body.     -   8. The method of any preceding clause, wherein the soak         temperature is within 20° C. and less than the solidus         temperature of the as-prepared aluminum alloy body.     -   9. The method of any preceding clause, wherein the soak         temperature is within 10° C. and less than the solidus         temperature of the as-prepared aluminum alloy body.     -   10. The method of any preceding clause, wherein the soak         temperature is within 5° C. and less than the solidus         temperature of the as-prepared aluminum alloy body.     -   11. The method of any preceding clause, wherein the second vol.         % of Fe-bearing particles in the as-solutionized aluminum alloy         body is at least 5% less than the first vol. % of Fe-bearing         particles in the as-prepared aluminum alloy body.     -   12. The method of any preceding clause, wherein the second vol.         % of Fe-bearing particles in the as-solutionized aluminum alloy         body is at least 10% less than the first vol. % of Fe-bearing         particles in the as-prepared aluminum alloy body.     -   13. The method of any preceding clause, wherein the second vol.         % of Fe-bearing particles in the as-solutionized aluminum alloy         body is at least 25% less than the first vol. % of Fe-bearing         particles in the as-prepared aluminum alloy body.     -   14. The method of any preceding clause, wherein the second vol.         % of Fe-bearing particles in the as-solutionized aluminum alloy         body is at least 50% less than the first vol. % of Fe-bearing         particles in the as-prepared aluminum alloy body.     -   15. The method of any preceding clause, wherein the second vol.         % of Fe-bearing particles in the as-solutionized aluminum alloy         body is at least 75% less than the first vol. % of Fe-bearing         particles in the as-prepared aluminum alloy body.     -   16. The method of any preceding clause, wherein the second vol.         % of Fe-bearing particles in the as-solutionized aluminum alloy         body is at least 90% less than the first vol. % of Fe-bearing         particles in the as-prepared aluminum alloy body.     -   17. The method of any preceding clause, wherein the aluminum         alloy body comprises 20-400 ppm Fe.     -   18. The method of any preceding clause, wherein the aluminum         alloy body comprises not greater than 3 wt. % Mg.     -   19. The method of any preceding clause, wherein the aluminum         alloy body comprises at least some Mg.     -   20. The method of any preceding clause, wherein the aluminum         alloy body comprises one of a 1xxx, 2xxx, 3xxx, 4xxx, 5xxx,         6xxx, 7xxx, and 8xxx aluminum alloy.     -   21. The method of any preceding clause, wherein the aluminum         alloy body comprises an aluminum alloy selected from the group         consisting of: a 1xxx aluminum alloy, a 3xxx aluminum alloy, and         a 5xxx aluminum alloy.     -   22. The method of any preceding clause, wherein the aluminum         alloy body comprises an aluminum alloy comprising at least 90         wt. % Al.     -   23. The method of any preceding clause, wherein, when measured         in accordance with an electrochemical cell test, a corrosion         resistance of an aluminum electrode alloy product produced using         the as-solutionized aluminum alloy body is greater as compared         to the corrosion resistance of a reference aluminum electrode         alloy product produced using a reference aluminum alloy body.     -   24. The method of any preceding clause, wherein the preparing         step (a) comprises working the aluminum alloy body into a sheet         or plate, the working comprising at least one of hot rolling and         cold rolling the aluminum alloy body.     -   25. The method of any preceding clause, wherein the preparing         step (a) comprises: forming a melt of an aluminum alloy; and         casting the melt to form the aluminum alloy body, wherein the         casting step comprises one of: (i) direct chill casting; (ii)         continuous casting; and (iii) shape casting.     -   26. The method of any preceding clause, wherein the preparing         step (a) comprises additively manufacturing the aluminum alloy         body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an example of an electrochemical cell that is configured for use in evaluating the corrosion of electrodes in an electrolyte in accordance with the present disclosure.

FIG. 2 is a graph showing hydrogen gas generation and vol. % of Fe-bearing particles for solutionized and non-solutionized alloys for four different alloy compositions.

DETAILED DESCRIPTION Examples

The following examples are intended to illustrate the invention and should not be construed as limiting the invention in any way.

Example 1—Preparing Aluminum Electrode Alloy Product Samples

Aluminum alloys 1-4, having the compositions shown in Table 1, below, were cast as ingots and rolled to the desired thickness.

TABLE 1 Composition of Ex. 1 Alloys (in ppm) Alloy Mg Fe 1 24200 5 2 25800 71 3 25200 95 4 24500 182

Four disks having the desired thickness (4-10 mm) and diameter (9.35 cm) were machined from each of the four ingots. Each disk had a sufficient cross-sectional surface area (i.e., 68.7 cm²) to provide a viable testing surface for immersion into an electrochemical cell (schematically depicted in FIG. 1) for the evaluation and assessment of corrosion within the range of operating conditions of the cell (e.g. time, temperatures, current, etc.). For each of Alloys 1-4, two of the four disks were solutionized at a soak temperature of 590° C. and for a soak time of 48 hours. For each of Alloys 1-4, the remaining two disks were not subject to the solutionizing step (b) of the disclosed method. Non-solutionized disks were designated as “reference” aluminum electrode alloy products, and solutionized disks were designated as “sample” aluminum electrode alloy products.

Example 2—Testing of the Aluminum Electrode Alloy Reference and Sample Products

The reference and sample disks were tested for corrosion resistance (hydrogen generation) via an electrochemical cell system (schematically depicted in FIG. 1). The electrochemical cell consists of a counter electrode and an aluminum electrode (the reference or sample) alloy product submerged in an aqueous electrolyte. The electrochemical cell is equipped with a mass-flow meter for measuring hydrogen gas (i.e., H₂) evolved from the aluminum electrode alloy product. Current is applied on the aluminum electrode alloy product, and flows through the electrolyte and into the counter electrode.

The reference and sample disks were tested according to the following procedure. A predefined temperature-and-current step control program was applied to the cell so that the hydrogen evolution rate was measured over a set range of operating temperatures, i.e. between room temperature and 100° C. and over a set of current densities, ranging from 0 to 300 mA/cm².

The reference and sample disks were run under identical conditions including electrolyte temperature, applied current, and test duration. Results were generated based on hydrogen gas generation, by accumulating the overall amount of hydrogen measured by the mass flow meter. The hydrogen generation was normalized to the surface area of each electrode. Without being bound by a particular mechanism theory, it is believed that the overall amount of hydrogen generated by the system corresponds to the corrosion reaction (undesired reaction). Thus, the less hydrogen produced, the more corrosion resistant the aluminum electrode alloy product is that is being evaluated.

As shown in FIG. 2, sample disks (i.e. solutionized) from Alloys 2, 3 and 4 generated less hydrogen (11.3, 14.4, and 53.2 cc/cm², respectively) than reference disks (i.e. non-solutionized) with the same composition (54.2, 75.5 and 115.1 cc/cm², respectively). Both sample and reference disks from Alloy 1 produced the same amount of hydrogen.

In some embodiments, higher amounts of undissolved impurities, such as iron, in an aluminum electrode alloy may result in an increased hydrogen generation (when compared to an aluminum electrode alloy having a lower amount of undissolved impurities).

However, without wishing to be bound by theory, it is believed that, due at least in part to the solutionizing, disclosed herein, at least some of the iron may be dissolved into solid solution, which is believed to improve the corrosion resistance (e.g. generate a lower amount of hydrogen when evaluated in an electrochemical half-cell test as set out in Example 2).

Furthermore, without being bound by a particular mechanism or theory, it is believed that addition of Mg as a purposeful alloying element to Fe-containing aluminum alloy bodies may result in higher amounts of undissolved iron (e.g., due at least partly to formation of Fe—Mg-bearing particles), and therefore a reduced corrosion resistance (increased hydrogen generation, increased corrosion of the aluminum electrode alloy products formed from such aluminum alloy bodies). Without being bound by a particular mechanism or theory, it is believed that the disclosed solutionizing of Fe-containing aluminum alloy bodies having Mg encourages dissolution of both Fe and Mg into solid solution, thereby suppressing formation of Fe—Mg-bearing particles. In this regard, the aluminum electrode alloys of the present disclosure are configured with up to 5.0 wt. % Mg, as discussed above. Thus, lower hydrogen generation (i.e., reduced corrosion) is achievable with the disclosed Fe-containing aluminum electrode alloy products having up to 0.06 wt. % Fe and up to 5.0 wt. % Mg, as compared to the baseline (i.e., reference, non-solutionized) Fe-containing aluminum electrode alloy products. Furthermore, lower hydrogen generation (e.g. reduced corrosion) with these aluminum electrode alloy products, as compared to baseline (i.e., reference, non-solutionized) aluminum electrode alloy products may be achieved at Fe levels of 5-182 ppm and Mg levels of not greater than 2.6 wt. %.

Example 3—Procedure for Calculating Volume Percent of Fe-Bearing Particles

The following is the procedure used for calculating the volume percentage of Fe-bearing particles in an Fe-containing aluminum alloy body:

Step 1. Preparation for Scanning Electron Microscope (SEM) Imaging

For each of the reference and sample disks that were not used for the electrochemical cell test of Example 2, sections were taken and then ground for about 30 seconds using progressively finer grit paper starting at 240 grit and followed by 320, 400, and 600 grit paper. After grinding, the samples were polished for about 2-3 minutes on cloths using a sequence of (a) 3 micron mol cloth and 3 micron diamond suspension, (b) 3 micron silk cloth and 3 micron diamond suspension, and (c) a 1 micron silk cloth and 1 micron diamond suspension. During polishing, an oil-based lubricant was used. Prior to SEM examination, a final polish was made using 0.05 micron colloidal silica for about 30 seconds, followed by a final rinse under water.

Step 2. SEM Image Collection

Using an FEI XL30 FEG SEM, or comparable FEG SEM, a minimum of 40 backscattered electron images were captured at both the center (T/2) and near the outer edge (sample surface) of the metallographically prepared (per step 1, above) sections, thus providing a minimum of 80 images total per section. The image size was 2048 pixels by 1600 pixels at a magnification of 1000×. The pixel dimensions were x=0.059 μm, y=0.059 μm. The accelerating voltage was 7.5 kV at a working distance of 7.5 mm and spot size of 5. The contrast and brightness was set so that the average matrix grey level of the 8-bit digital image was approximately 128 and the darkest and brightest phases were 0 (black) and 255 (white), respectively.

Step 3. Discrimination of Secondary Phase Particles

The average matrix grey level and standard deviation were calculated for each SEM image. The average atomic number of the secondary phase particles of interest is higher than the matrix (the aluminum matrix), so the secondary phase particles appeared lighter in the image representations. The pixels that make up the particles were defined as any pixel that had a grey level higher than (>) the average matrix grey level plus 3.5 standard deviations. This critical grey level was defined as the threshold. A binary image was created by discriminating the grey level image to make all pixels higher than the threshold to be white (255) and all pixels at or lower than the threshold to be black (0).

Step 4. Removal of Small Particles

Any white particle that had 4 or fewer pixels was removed from the binary image by changing its color to the background color (black).

Step 5. Calculation of Volume Percent of Fe-Bearing Particles:

Once each image was converted into solely black and white pixels, the area fraction of particles was calculated as the total number of white pixels divided by the total number of pixels. This fraction was calculated for each image for a single location, and then averaged. The total area fraction (AF) for a given sample was then calculated as a weighted average of the area fraction at T/2 and near the surface, where the near surface number was weighted twice because it occurred twice in the sample. Area fraction was then converted into a percent by multiplying by 100. The volume percent of the Fe-bearing particles in the product was then determined based on Equation (I):

Fe-Bearing Particles (vol. %)=100*(AF_(T/2)+2*AF_(S))/3

AF=# WhitePixels/# TotalPixels  (I)

As shown in FIG. 2, sample disks from Alloys 1-4 all had a lower vol. % of Fe-particles (0.00014, 0.00003, 0.00000, and 0.01022 vol. %, respectively) as compared to reference disks of Alloys 1-4 (0.0046, 0.01115, 0.02335, and 0.04401 vol. %, respectively).

In some embodiments, higher amounts of undissolved iron in an aluminum alloy body may result in increased vol. % of Fe-bearing particles (when compared to an aluminum alloy body having a lower amount of undissolved iron). However, without wishing to be bound by theory, it is believed that, due at least in part to the solutionizing disclosed herein, at least some of the iron may be dissolved into solid solution, which is believed to reduce the vol. % of Fe-bearing particles and thereby improve the corrosion resistance, as described above in Example 2.

While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art. Further still, the various steps may be carried out in any desired order (and any desired steps may be added and/or any desired steps may be eliminated). 

What is claimed is:
 1. A method comprising: (a) preparing an aluminum alloy body for solutionizing, wherein the aluminum alloy body comprises: (i) not greater than 0.06 wt. % Fe, wherein at least some Fe is present; (ii) not greater than 5.0 wt. % Mg; (iii) the balance aluminum and unavoidable impurities; and (iv) a first vol. % of Fe-bearing particles; and (b) solutionizing the as-prepared aluminum alloy body, wherein the solutionizing step (b) comprises dissolving at least some of the Fe-bearing particles into solid solution, thereby decreasing the first vol. % of Fe-bearing particles to a second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body.
 2. The method of claim 1, wherein the aluminum alloy body is suitable for use as an aluminum electrode alloy product.
 3. The method of claim 1 comprising: determining, prior to the solutionizing step (b), conditions for the solutionizing step (b), wherein: (i) the conditions include a soak temperature range of from 515° C. to a Temperature2 (° C.); (ii) a value of Temperature2 is dependent on an actual wt. % Mg of the aluminum alloy body; and (iii) Temperature2=644.6° C.−[15.73*(actual wt. % Mg)]; and completing the solutionizing step (b) according to the determining step.
 4. The method of claim 3 comprising selecting a value for a target temperature (° C.) within the soak temperature range, wherein: (i) the conditions include a soak time range of from Time1 (hours) to Time2 (hours); (ii) Time1=1.2141×10⁸*e{circumflex over ( )}−(0.032516*target temperature); and (iii) Time2=1.4467×10¹⁰*e{circumflex over ( )}−(0.032828*target temperature).
 5. The method of claim 1 comprising: determining, prior to the solutionizing step (b), conditions for the solutionizing step (b), wherein: (i) the conditions include a soak temperature within 50° C. and less than a solidus temperature of the as-prepared aluminum alloy body; and completing the solutionizing step (b) according to the determining step.
 6. The method of claim 5, wherein the soak temperature is within 40° C. and less than the solidus temperature of the as-prepared aluminum alloy body.
 7. The method of claim 6, wherein the soak temperature is within 30° C. and less than the solidus temperature of the as-prepared aluminum alloy body.
 8. The method of claim 7, wherein the soak temperature is within 20° C. and less than the solidus temperature of the as-prepared aluminum alloy body.
 9. The method of claim 8, wherein the soak temperature is within 10° C. and less than the solidus temperature of the as-prepared aluminum alloy body.
 10. The method of claim 9, wherein the soak temperature is within 5° C. and less than the solidus temperature of the as-prepared aluminum alloy body.
 11. The method of claim 1, wherein the second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body is at least 5% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body.
 12. The method of claim 11, wherein the second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body is at least 10% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body.
 13. The method of claim 12, wherein the second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body is at least 25% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body.
 14. The method of claim 13, wherein the second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body is at least 50% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body.
 15. The method of claim 14, wherein the second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body is at least 75% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body.
 16. The method of claim 15 wherein the second vol. % of Fe-bearing particles in the as-solutionized aluminum alloy body is at least 90% less than the first vol. % of Fe-bearing particles in the as-prepared aluminum alloy body.
 17. The method of claim 1, wherein the aluminum alloy body comprises 20-400 ppm Fe.
 18. The method of claim 1, wherein the aluminum alloy body comprises not greater than 3 wt. % Mg. 